Vertical recording has long been considered for use in ultra-high density storage applications. 200 G bits per square inch is considered feasible for such a design. In its application, the transducer consists of a reader such as a spin valve (SV), magnetic tunneling junction (MTJ) and current perpendicular to plane (CPP), giant magneto-resistance (GMR) device, and a writer, typically a single pole construction, as illustrated in FIG. 1. Write coil 11 is encapsulated between upper write pole 12 and shared pole 13, with the latter providing a flux return path for the write flux 14. As can be seen, the magnetic flux in region 19 is perpendicular to recording layer 17 with the magnetic circuit being completed inside keeper layer 18.
The read portion of the device consists of the read head 15 itself and lower read head shield 16, with shared pole 13 serving as the upper read head shield. The practice of sharing the lower flux return layer with the upper head shield is a legacy of earlier longitudinal recording technology where the write field is generated across a gap between the two poles of the recording assembly. This had the advantage of reducing the separation between writing and recording heads and, additionally, saved one layer.
Although the advantage of saving one layer continues to be part of the prior art design that is illustrated in FIG. 1, there are two disadvantages associated with it. The separation W1 between the write and read heads has been increased and, because of the close proximity of the two head shields, 13 and 16, a certain amount of return flux 20 will flow back through lower shield 16, exposing the read head 15 to a less than optimum environment. The read head 15 will sense some write flux which will interfere with the normal servo signal to produce a spurious position error signal.
The distance between read and write elements needs to be large enough to allow room for the writing coil 11 (including two layers of insulation) and also to give a good vertical write field profile. This requirement calls for a read-to-write distance in the order of 10 μm. When this is combined with a swing arm actuator, the read-to-write track off-set can be rather large. For a track density of 160 ktpi and total ID-to-OD (inside to outside diameter) swing of 20 degrees, the off-set will be about 1.7 μm, or about 10 tracks. Although micro jag can be utilized to cope with this offset, the system performance will be greatly degraded. It is, therefore, imperative to reduce this distance, while maintaining a good vertical write field profile Note that the term ‘jag’ refers to micro-stepping of the head and the jagging distance is the departure from their aligned positions of the read and write heads.
A routine search of the prior art was performed with the following references of interest being found:
In U.S. Pat. No. 6,038,106, Aboaf et al. show a write head that does not use a shared pole as do Schewe et al. in U.S. Pat. Nos. 4,703,382 4,974,110 (Kanamine et al.), U.S. Pat. No. 4,546,398 (Toda et al.), U.S. Pat. No. 4,652,956 (Schewe) and U.S. Pat. No. 5,719,730 (Chang et al.) are related MR head patents.